A nanostructured porous carbon/MoO2 composite with efficient catalysis in polysulfide conversion for lithium–sulfur batteries

Abstract

Lithium–sulfur batteries are considered as the next generation of energy storage systems because of their high theoretical specific capacity and energy density. Unfortunately, the sluggish reaction kinetics, weak adsorption toward to lithium polysulfides, and slow lithium ion diffusion impede the smooth electrochemical process, resulting in the lithium–sulfur batteries with the unsatisfactory cycling stability and rate performance. Since it is recognized that polar metal oxides and doped nitrogen in carbon materials have chemical interaction with lithium polysulfides, a nanostructured nitrogen-doped porous carbon/MoO2 composite is synthesized through a simple hydrothermal method by using graphene oxide nanoribbon and phosphomolybdic acid hydrate as precursors. The porous nanostructure promotes the charge and mass transport, while MoO2 nanoparticles immobilize lithium polysulfides via strong chemisorption and enhance the redox kinetics of polysulfides owing to the efficient catalytic activity in liquid–solid boundary. Consequently, the as-obtained nanostructured porous carbon/MoO2-based sulfur cathode exhibits low polarization, high initial discharge capacity (1403 mAh g−1 at 0.1 C), good rate capabilities (584 mAh g−1 at 4 C), and impressive cycling performance at 1 C (503 mAh g−1 after 500 cycles with capacity fade rate of 0.07% per cycle).